Fulltext Search - Problems with 'Umlauts' like ÃƒÂ¤Ãƒ

I don't find words with umlauts like ÃƒÂ¤ÃƒÂ¼ÃƒÂ¶… with the fulltext search in the doucment content. I only find documents that have such characters in the name. Does andybody has the same problem, or better, does andybody solved this issue :)